Load sensing system

ABSTRACT

A programmable microcomputer controlled load sensing system for maximizing the cleaning efficiency of particulate raw materials such as sand, gravel, rock, ores, etc. in a log washer by sensing the weight of the aggregate in the log washer tank and adjusting the angle of inclination of the tank for cleaning efficiency. The system includes a log washer tank pivoted at its lower end and supported by hydraulic cylinders at its upper end. A high/low pressure sensor detects changes in the weight of the load by changes in hydraulic fluid pressure communicated to the microcomputer, and raises or lowers the upper end of the tank when the programmed low or high pressure limits are exceeded through solenoid activated hydraulic valves.

[0001] This application is a continuation-in-part of Ser. No. 10/295,846filed on Nov. 18, 2002.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates generally to aggregate materialcleaning systems. More specifically, the invention is a fully automatic,load sensing system for a log washer that is used for cleaning aggregatematerials, such as rocks, gravel, sand, and ores to remove dirt andwaste materials. The system hydraulically changes the angle of inclineof the washer tank to ensure that the washer tank is properly loadedwith the solids for efficient cleaning action.

[0004] 2. Description of the Related Art

[0005] The related art of interest describes various washing andweighing apparatus, but none recognizes the washing inefficiency problemand none discloses the present invention. There is a need for log washerfor washing sand, gravel, ores, and similar particulate material tomaximize the cleaning action based upon variations in the weight of theload being cleaned. The problem exists because in conventional logwashers the inclination angle of the washer tank is fixed, whereas theload fluctuates in weight. As a general rule, if the angle of incline ofthe tank is increased, production is decreased, but the cleansing actionof the washer is increased. Currently, the only way to vary the angle ofincline is by manually increasing or decreasing the height of thestructure supporting the washer tank, a labor intensive process whichinvolves temporarily shutting down the log washer while the supports areadjusted. Therefore, by automatically adjusting the incline of thewasher tank according to the load of solids, adequate cleaning isaccomplished to maximize the efficiency of the washing process. Therelated art will be discussed in the order of perceived relevance to thepresent invention. No art discloses the critical feature ofautomatically adjusting the incline of the washer or separator tank toadjust the weight of the solids load to the washer.

[0006] U.S. Pat. No. 3,807,558 issued on Apr. 30, 1974, to Alton B. Hammdescribes an apparatus for separating lightweight debris from sand,gravel and logs comprising the flowing of water at a high velocity in arestricted flow path to one side of the rotating auger and rotating thelogs. The granular and aggregate material is discharged into the waterflow for removing unwanted lightweight debris prior to the movement ofthe granular material into the zone of operation of the auger of thesand screw or rotating logs of the log washer. The inclination of the,apparatus is supported by fixed supports. The apparatus isdistinguishable for requiring a restricted water flow path and fixedsupports for its inclination angle.

[0007] Japan Patent Application No. 7-253340 published on Oct. 3, 1995,for Toshihiko Miyashita describes an apparatus which can automaticallyperform an aggregate washing step in a pivotal mixing container with aspout, and emptying the aggregate material and liquid. The washerapparatus has a pair of supporting legs on a stage, and a base pad thatmay be rotated via a pivotal shaft in a vertical direction by thesupporting legs to empty the contents. The aggregate mixing containerhas a mixing blade within rotated by a first drive motor which rotateswith the container. The second drive motor rotates the mixing containerand the first drive motor. The apparatus is distinguishable for beinglimited to a rotatable emptying feature for a mixing chamber.

[0008] U.S. Pat. No. 4,234,415 issued on Nov. 18, 1980, to Enrique deTuya Casuso describes an apparatus for separating mixed solids ofdifferent specific gravities by means of a liquid medium comprising arotatable frusto-conical separation chamber having a lighter solidoutlet at one end, and a heavier solid outlet at the opposite end. Apair of frusto-conical chamber may be utilized to separate solids ofthree different specific gravities. The apparatus is distinguishable forits structural difference and its different objective of separatingmixed solids of at least two different specific gravities.

[0009] U.S. Pat. No. 5,868,256 issued on Feb. 9, 1999, to Maynard A.Teppo describes a rotary clay material refiner apparatus comprising ahorizontal rotating drum into which clay material and water are fed. Theclay material and water form a slurry which is agitated by lifterswithin the drum. A series of adjustable lifters with the drum refine theslurry by lifting aggregates and rocks out of the slurry and dischargingthem out of the refiner apparatus. The refined slurry exits the drumthrough an opening and further processed. The apparatus isdistinguishable for being confined to a horizontal rotating drum andrequiring two separation steps.

[0010] U.S. Pat. No. 2,489,161 issued on Nov. 22, 1949, to WilliamScholes describes a gravity liquid separator apparatus for theseparation of unspecified granular or lump material, comprising a tankminus an outlet wall and the bottom inclined up from the deep feedingend, wherein the material is fed from the bottom of the deep end by acontinuous belt passing through an opening with a trailing rubber fabricsealing flap or an inflated pneumatic tube to minimize leakage. A rotaryscraper is positioned midway in the apparatus. The apparatus isdistinguishable for requiring a rotating material transporting beltwithin the tank.

[0011] U.S. Pat. No. 2,336,991 issued on Dec. 14, 1943, to Chester I.Leveke describes an apparatus for removing dirt, clay, shale, coal, andthe like material from gravel comprising an inclined elongated troughhaving a square cross-section, a substantially open top, a bottom graveloutlet in the forward end and a hopper, and a grave escape slot at theopposite end. A centered rotating cylindrical agitator has agitatingblades and three portions of decreasing diameter to the outlet. Theapparatus is distinguishable for lacking any adjustable inclinationmeans.

[0012] U.S. Pat. No. 1,972,195 issued on Sep. 4, 1934, to Marmakuke J.Lacey, Jr. describes an ore washer apparatus for washing ores such asphosphates, manganese and iron or concrete aggregates containing clay,chips, and silt in a fixed inclined frame. The moving gear comprises 5parallel chains bearing plow share blades rotating on 3 sprocket wheelsto define a triangle as viewed from the side. The ores are added in thebaffled rear end and pushed to the front end in water for dischargingout of the water via a discharge throat. The apparatus isdistinguishable for requiring an immovable fixed tank.

[0013] U.S. Pat. No. 1,695,021 issued on Dec. 11, 1928, to Samuel R.Puryear describes an apparatus for separating solids comprising asubstantially rectangular inclined tank with an enlarged rear end andtwin screws. The solids such as mud balls mixed with gravel, lignite,coal, shale, and shells are fed with water from a chute into the rearend of the tank. The lighter materials are flushed by water jets towardan adjustable weir and into a perforated conduit leading to a reartrough. The twin screws carry the heavier material up the inclined tankout of the water and into a delivery chute. The apparatus isdistinguishable for requiring a rear separation trough and directionaljets of water.

[0014] U.S. Pat. No. 2,025,841 issued on Dec. 31, 1935, to Charles H.Young describes an apparatus for washing gravel to remove shale,lignite, bark, water-logged wood, and coal comprising an inclined tankon a frame support, and having a pair of screw conveyors which acceptthe heavier gravel feed from a shallow pan which discharges the heaviermaterial in the rear. The screw conveyors move the gravel through thewater to an outlet. Jets of water are also supplied continuously upwardthrough the mixture from a bottom located pipe. The apparatus isdistinguishable for requiring a fixed support.

[0015] U.S. Pat. No. 4,448,678 issued on May 15, 1984, to Cecil C.Gentry describes an inclined treatment trough having a two-sectionconveyor screw consisting of a notched screw in the front and a helicalscrew. In the rear of the trough, crushed lignite is fed into a settlingpool of water having weir in the rear wall covering an exiting stream,while above the stream waste tailings flow over the rear wall. Water issprayed above the trough. The lignite product exits at the front portionof the trough. Fixed supports are illustrated to obtain the inclinationangle of the trough. The apparatus is distinguishable for requiring atwo-section conveyor screw and fixed supports for inclining the trough.

[0016] U.S. Pat. No. 1,609,652 issued on Dec. 7, 1926, to John L.McQueen describes a log washer apparatus comprising twin screws havingintermeshing paddles with cutting edges for washing sand, gravel, ores,and manganese to remove clay, dirt and waste matter. The apparatus isdistinguishable for requiring specific log washer screws.

[0017] U.S. Pat. No. 2,050,458 issued on Aug. 11, 1936, to MelvinOvestrud et al. describes a wheeled apparatus for treating quarried rockor pit run gravel to produce aggregates for concrete construction workcomprising, in sequence, an upper scrubber chamber (inclined downward)receiving the raw feed, a coarse and fine particle conveyor, and adehydrator chamber with an endless conveyor belt. A screen at the end ofthe scrubber chamber filters the smaller particles that pass down ahopper to a crusher. The apparatus is distinguishable for requiringmultiple separating elements and a crusher, and lacking any adjustmentof the inclination of the scrubber chamber.

[0018] U.S. Pat. No. 2,324,549 issued on Jul. 20, 1943, to Paul L.Wigton describes a spiral ore pulp classifier apparatus comprising anupwardly inclined open tank on fixed supports being fed ore pulp intothe tank having a pool of water and a spiral conveyor. The pool end ofthe tank has an upper outlet for slime and a bottom outlet for a drain.Sand is discharged from the front end. The apparatus is distinguishablefor requiring a fixed inclination.

[0019] U.S. Pat. No. 5,992,776 issued on Nov. 30, 1999, to Gianni B.Arcaini et al. describes a process for processing ash from the massburning of municipal waste utilizing various apparatus comprising ashear-force shredder for the size reduction of bulky items, impactcleaning of ferrous metal items, and a rotary washer for cleaningnon-ferrous materials. The ash is sent through an air separation unit toremove paper, wood, plastic, and other unburned debris before passingthe ash to an eddy current separator for non-ferrous material removal.The ash is free of metal values, unburned materials and unshreddables,but must be treated to immobilize certain heavy metals. The ash isrecycled through a closed loop to increase removal efficiency of themetals and the homogeneous nature of the recovered treated ashaggregate. The apparatus used in this process is distinguishable forfailing to require an inclined separator.

[0020] U.K. Patent Application No. GB 2,280,384 published on Jan. 2,1995, for Patrick Brogan describes a horizontal bucket wheel sand washerwith a submerged recovered fine aggregate transporter apparatus limitingits movement to prevent agitating the flowing water. The submergedtransporter apparatus may be a screw conveyor or a multi-bladed scrapermounted on a frame reciprocated by rams and guided in an elevated returnmovement over pivoted cams. The apparatus is distinguishable for itsrequired horizontal structure.

[0021] Japan Patent Application No. 8-168693A published on Jul. 2, 1996,for Kiyohiro Taniguchi describes an inclined apparatus to prevent fineaggregate such as sand from being mixed with the muddy water beingcarried off by a conveyor belt when the fine aggregate such as sand istaken out from a water tank by a belt conveyor device. The silt iscollected in a hopper and passed to a conveyor belt while the muddywater is collected in a separate container. The apparatus isdistinguishable for lacking any change in the inclination.

[0022] Japan Patent Application No. 9-203407A published on Aug. 5, 1997,for Yoshimichi Ishii et al. describes a screw conveyor and washerapparatus comprising multiple washers connected in a single line viamicrojoints. Multiple screws with individual washers in a single lineare attached to a supplying means of unknown material. Each washer isseparated in turn at its microjoint part so that the screw with itswasher is supplied. The apparatus is distinguishable for its requiredmicrojointed structure.

[0023] German Patent Application No. DE 199 28 287 A1 published on Dec.28, 2000, for Steffen Prieske describes a method for disposing excavatedwaste material by conveying the waste material to a buffer container fordelivery to a drum washer, wherein coarse particles are separated fromfiner particles, and the overflow is supplied to a hydro-cyclone screenapparatus for recycle of the fluid and the disposal of the solids to adump. The apparatus is distinguishable for requiring a drum washer and ahydro-cyclone screen.

[0024] None of the above inventions and patents, taken either singly orin combination, is seen to describe the instant invention as claimed.Thus, a load sensing system solving the aforementioned problems isdesired.

SUMMARY OF THE INVENTION

[0025] The present invention is directed to a load sensing system forlog washers for washing coarse materials such as rocks, sand, gravel,and ores in order to improve the washing process in an open inclinedtank. A conventional log washer apparatus is measurably affected by theangle at which the washer tank is fixed. If the washer load becomes toolight for the angle of incline of the tank, the cleansing action becomesinadequate. Conventional log washer tanks have no automated mechanismfor automatically adjusting the inclination of the tank in response tochanges in the quantity of the load. The present invention automaticallychanges the angle of incline of the washer apparatus by adding hinges tothe lower portion of the tank and hydraulic cylinders to raise and lowerthe upper portion of the tank in response to changes in pressure causedby the load in the washing tank.

[0026] In the load sensing system of the present invention, the lowerend of the log washer tank is mounted on a hinged support, and the upperend is supported by a pair of hydraulic cylinders or rams. A high-lowpressure sensor device senses changes in the weight of the load in thetank and activates solenoid switches connected to hydraulic valves andto an electric motor that activates a hydraulic pump in order to raiseor lower the hydraulic rams as required to maximize the washing action.

[0027] If the hydraulic pressure is low as read by the high/low pressuresensor, the total weight of the material in the washer tank isconsidered below the optimum weight desired. Therefore, the low pressuresensor switch will activate a hydraulic pump by a starter motor and ahydraulic valve. This action will create the hydraulic flow that flowsthrough a flow divider circuit to a pair of hydraulic cylinders toincrease the incline of the washer tank. The elevated washer tank endwill rise until the load weight increases, or until a high limit switchindicates that maximum extension of the rams is reached. The firsthydraulic valve will then close to hold the washer tank position. Whenthe load increases in weight, the high-low pressure sensor will sensethis condition and will activate a latching relay device in the tanklowering circuit. The lowering valve is activated to allow the hydraulicoil back through the divider-combiner valve to the oil tank. Thelowering valve will lower the washer tank as long as the load in thewasher tank is sufficient to activate the high/low pressure sensor.

[0028] If the bottommost incline value is not reached, and the loaddecreases, the low pressure sensor will activate the latching relay inthe raising circuit to increase the inclination angle of the washertank. If the washer tank load reaches the lowest incline limit, thesystem will operate at the setting of the inclination angle until thelow limit sensor detects the lower pressure of a light load, andactivates the latching relay in the tank raising circuit. A needle valveregulates how rapidly the tank lowers. A high pressure relief valvediverts or bleeds off hydraulic oil to return to the oil reserve tank,if the high pressure limit setting is reached. A check valve is requiredto ensure that the hydraulic oil does not flow in the oppositedirection. Thus, the load sensing system operates to maximize thewashing process for an open inclined tank.

[0029] Accordingly, it is a principal object of the invention to providea load monitoring system for monitoring the solid load relative to thequantity of water added to a log washer apparatus.

[0030] It is another object of the invention to maximize the washingefficiency of a log washer tank by monitoring the load to raise or lowerthe inclination of the wash tank.

[0031] It is a further object of the invention to change the inclinationof the wash tank by measuring the load to maximize the washingefficiency process.

[0032] Still another object of the invention is to utilize a hydraulicsystem for changing the inclination of the washer tank.

[0033] It is an object of the invention to provide improved elements andarrangements thereof for the purposes described which is inexpensive,dependable and fully effective in accomplishing its intended purposes.

[0034] These and other objects of the present invention will becomereadily apparent upon further review of the following specification anddrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0035]FIG. 1A is an environmental, perspective side view of a portion ofa load sensing system applied to the loading of a particulate washingtank according to the present invention.

[0036]FIG. 1B is an enlarged-scale perspective view of the FIG. 1A loadsensing apparatus according to the present invention.

[0037]FIG. 2 is an enlarged-scale elevational view of the balance of themonitoring employed in the system according to the present invention.

[0038]FIG. 3 is a schematic diagram of the various units employed in thehydraulic system according to the present invention.

[0039]FIG. 4 is a schematic circuit diagram illustrating the operationof a modified load sensing system according to the present invention.

[0040]FIG. 5 is an elevational view of the lower end of the washing tankshowing the pair of hinges required for adjusting the inclination of thewashing tank.

[0041] Similar reference characters denote corresponding featuresconsistently throughout the attached drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0042] The present invention is directed in FIGS. 1A, 1B, 2, and 3 isdirected to a weight sensing system 10 for a log washer tank 12 foradjusting the inclination of the tank in response to changes in the loadof particulate material to be washed in the tank 12, shown partially inFIG. 1A. In FIGS. 1A and 1B, an electrical control box 14 is connectedto a pressure module 18 and to a high/low pressure sensor switch 30. Aboxed divider/combiner valve 20 is depicted in FIGS. 2 and 3 having aplurality of hydraulic lines 22 connected to a hydraulic pump andreservoir, and also to a pair of hydraulic cylinders 24 for raising andlowering the tank 12. The hydraulic cylinders 24 are mounted below theupper end of the water tank 12 and on opposite side of the tank, onlyone of the cylinders 24 being shown in FIG. 1A, the opposite side beingsymmetrical. As shown, the cylinders are preferably mounted with thetank 12 bearing on the bottom end of the cylinder, and the ram or pistonrod resting on a fixed support.

[0043] As shown in FIG. 3, the divider/combiner valve 20 the hydraulicpressure actuating the two hydraulic cylinders 24 equally. Apredetermined high elevation limit and a low elevation limit in terms ofthe ram or piston rod travel is set by conventional mechanical leverswhich trigger high-low electrical switches 26. A hydraulic line from thedivider/combiner valve 20 communicates with a pressure gauge 28 and ahigh/low pressure sensor switch 30. The hydraulic line divides to ahigh/low pressure circuit 32 and a low pressure circuit 34. The highpressure circuit 32 includes in sequence a one-way check valve 36 toprevent back flow from the cylinders 24 to the pumps 54, but which willopen on excessive pressure from the pump 54 to raise the cylinders 24, anormally closed hydraulic valve/solenoid element 38, and a high pressurerelief valve 40 which dumps off excessive hydraulic pressure throughline 42 to the low pressure circuit 34. The low pressure circuit 34consists of a normally closed hydraulic valve/solenoid 44, a needlevalve 46, a hydraulic fluid return line 48 that also receives fluid fromthe hydraulic line 42 to flow to the hydraulic oil supply tank 50. Theneedle valve 46 regulates how quickly the tank 12 is lowered. Whenhydraulic fluid is required for extending the hydraulic cylinders 24 bysignal from the high/low pressure sensor switch 30, an electric ordiesel motor 52 is energized by the electrical control box 14 to startand run an auxiliary hydraulic pump 54 to increase the hydraulicpressure to the predetermined degree of inclination.

[0044] As the load in the upper end of the washer tank 12 increases, theadditional weight bearing on the bottom ends of hydraulic cylinders 24increases hydraulic fluid pressure in the system. When the hydraulicpressure exceeds a predetermined high pressure limit, the high/lowpressure sensor switch triggers the solenoid connected to the normallyclosed hydraulic valve/solenoid 44 in the return line 34 to releasefluid from the cylinders 24, thereby lowering the tank 12 until thehydraulic pressure does not exceed the high pressure limit or until themaximum low level limit of the ram or the piston rod travel is reached.This action increases production flow through the log washer tank 12,but adequate cleaning is maintained by the greater quantity ofparticulate matter providing the scrubbing action in the tank. When thehydraulic pressure is under a predetermined high pressure limit, thehigh/low pressure sensor switch 30 triggers the solenoid connected tothe hydraulic valve 38 to open it to increase fluid flow into thehydraulic cylinders 24, thereby raising the tank until the hydraulicpressure exceed the low pressure limit or until the maximum high levellimit of the ram or piston rod travel is reached. The action slowsproduction flow through the log washer tank 12, but increases thescrubbing period to compensate for the reduced volume of particulatematerial to maintain adequate cleaning of the particulates.

[0045] Alternatively, the high/low pressure sensor switch 30 formeasuring variations in hydraulic pressure under differing loads can bereplaced by a sensor that measures the variations in amperage requiredto drive the logs at constant speed under differing load conditions.

[0046]FIG. 4 shows a partial schematic diagram of the electrical controlsystem 56 for raising and lowering the hydraulic cylinders 24 byactuating valves 92 and 94, respectively. The circuit 56 includes anelectronic pressure sensor 58 that sends an appropriate signal to theprogrammable logic unit or microcomputer 60. The microcomputer isprogrammed to indicate that if the load in the tank 12 is lighter thanthe normal weight range, a signal will be transmitted by line 83 to thelight load indicator contactor coil device 84 to energize its closure tocomplete the circuit back to the microcomputer 60 by line 85. Currentfrom the coil device 84 is initiated to energize the electric motor 86by line 87 to increase the hydraulic pressure in the system by pump 88.Now, the microcomputer 60 will energize the second contactor coil device90 by line 91 to close and complete its circuit back by line 93 to themicrocomputer 60. The current from coil device 90 will energize and openthe hydraulic raising valve coil 92 to raise the incline of the tank 12to increase the washing efficiency of the light load. Once the loadincreases to the desired preset limit of the logic controller unit 60,the logic controller unit will stop the current to both the light loadindicator contactor 84 by line 83 and the coil contactor device 90 byline 91. The washer tank 12 will operate at this angle of inclinationuntil the microcomputer 60 receives a signal that falls within theoperating parameters of the program to lower the incline according tothe load in the washer tank 12. When this signal is received, themicrocomputer 60 will initiate a signal from an output terminal to acoil contactor unit 94 to energize it to complete the circuit back tothe microcomputer 60. Current from the coil contactor unit 96 willenergize the opening of the lowering hydraulic valve coil 94 to returnthe oil from the hydraulic cylinders to the hydraulic oil reservoir andcause the lowering of the inclination of the washer tank 12. The washertank will lower until the load falls back into the preset operatingrange parameters or until the load reaches the preset lower limit. Now,the washer tank 12 may raise or lower according to the position it is inand the preset operating conditions.

[0047] Thus, a log washing tank that can be inclined according to presetprogrammed conditions of the measured load by a microcomputer system tooperate the hydraulic cylinders has been shown which is fully effective.

[0048] It is to be understood that the present invention is not limitedto the embodiment described above, but encompasses any and allembodiments within the scope of the following claims.

I claim:
 1. A programmable microcomputer controlled load sensing systemfor a log washer apparatus for washing off aggregate material,comprising: a log washer tank having a pivotally mounted lower end andhaving an upper end; a pair of hydraulic cylinders, each hydrauliccylinder having a cylinder base depending from the upper end of the logwasher tank and a piston rod attached to a fixed ground support, saidhydraulic cylinders disposed on opposite width sides of the log washertank; a combiner/divider valve connected to said pair of hydrauliccylinders; a hydraulic pump and a hydraulic fluid reservoir connected tothe combiner/divider valve for pumping hydraulic fluid to and receivingsaid fluid from said combiner/divider valve for extending and retractingthe piston rods; an electronic pressure sensor disposed between saidhydraulic pump and said combiner/divider valve, the sensor having afirst state when hydraulic pressure exceeds a high pressure limit, asecond state when hydraulic pressure falls below a low pressure limit,and a third state when hydraulic pressure is between the high pressureand low pressure limits as detected by a programmable microcomputer;raising means for extending the piston rods of the pair of hydrauliccylinders when hydraulic pressure falls below the low pressure limit asdetected and controlled by the programmable microcomputer; and loweringmeans for retracting the piston rods of the pair of hydraulic cylinderswhen hydraulic pressure is above the high pressure limit as detected andcontrolled by the programmable microcomputer; whereby the log washertank is raised and lowered to an angle of incline with only theaggregate material load by the programmable microcomputer to promoteefficient washing in response to changes in weight of each load.
 2. Theprogrammable microcomputer controlled load sensing system according toclaim 1, further comprising a check valve disposed between saidhydraulic pump and said combiner/divider valve for preventing back flowof hydraulic fluid through said hydraulic pump.
 3. The programmablemicrocomputer controlled load sensing system according to claim 1,further comprising a high pressure relief valve disposed between saidhydraulic pump and said combiner/divider valve for diverting hydraulicfluid to said hydraulic reservoir when hydraulic pressure produced bysaid hydraulic pressure produced by said hydraulic pump exceeds a highpressure limit as controlled by the programmable microcomputer.
 4. Theprogrammable microcomputer controlled load sensing system according toclaim 1, wherein said raising means comprises a hydraulic valve disposedbetween said hydraulic pump and said combiner/divider valve, thehydraulic valve having a solenoid connected to said high/low pressuresensor for opening and closing the hydraulic valve.
 5. The programmablemicrocomputer controlled load sensing system according to claim 1,wherein said lowering means comprises a hydraulic valve disposed betweensaid hydraulic reservoir and said combiner/divider valve, the hydraulicvalve having a solenoid connected to said high/low pressure sensor foropening and closing the hydraulic valve.
 6. The programmablemicrocomputer controlled load sensing system according to claim 1,further comprising a needle valve disposed between said combiner/dividervalve and said hydraulic reservoir for regulating the flow rate ofhydraulic fluid to said hydraulic reservoir.